The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Hybrid vehicles, as compared to standard vehicles that are driven by an internal combustion engine (ICE), can provide improved fuel economy and reduced emissions. Hybrid electric vehicles achieve high fuel mileage by combining a battery-powered electric motor-generator (MG) with a highly efficient heat engine, typically an ICE. Parallel hybrid electric vehicles use power from both the heat engine and the electric engine to drive the wheels of the vehicle.
During varying driving conditions, hybrid vehicles alternate between separate power sources, depending on operating efficiencies of each power source. For example, a hybrid electric vehicle may alternate between an ICE and an MG. The ICE may be shut down during a stopped or idle condition, while the MG is used for propulsion. The ICE may be restarted when an increase in power is demanded. The shut down of the ICE conserves on fuel usage.
An on-board engine computer controls when the ICE and the MG are used to achieve peak efficiencies under different driving conditions. The MG may function both as a motor, delivering torque to the drive wheels, and as a generator, powering a vehicle electrical system and charging vehicle batteries. When the MG is functioning as a generator, the MG may be powered by the ICE or from the wheels of the vehicle. When powered by the ICE a belt is often used to transfer rotational energy from the ICE to the MG. The belt may also be used by the MG to reduce the speed of the ICE, referred to as braking the engine, and to start the ICE.
The belt can slip on pulleys that are coupled to the ICE and the MG. Belt slippage can negatively affect powertrain operating performance and emission performance of a hybrid vehicle. Belt slippage can be due to a frayed or worn belt, an improperly installed or tensioned belt, an improperly functioning tensioner, a warn or defective pulley, an out-of-alignment between pulleys, an improperly installed tensioner, etc.